1. Field of the Invention
This invention pertains generally to a “brain reading” process that can be used to decode the contents of sensory and cognitive systems of the human brain in order to read out an observer's subjective perceptual or cognitive experience.
2. Description of Related Art
Conventional brain decoding approaches are designed for classification, which poses decoding as a categorization problem. For example, a classifier designed for decoding perceptual states would take brain activity elicited by a stimulus that had been drawn from a small number of known categories (e.g., faces, places, animals) and determine from which of those specific categories the stimulus had been drawn. Classification is accomplished by constructing a discriminant function (typically linear) that can discriminate the brain activity evoked by each stimulus class. It has been demonstrated that perceptual classification is possible when the classifier was trained previously on the specific classes that are to be identified. The standard classifier approach is limited in a number of critical ways. First, it can only be used to identify categories of stimuli that were actually used to train the classifier. It cannot be used to classify images that belong to novel (i.e., untrained) classes. Second, the conventional classifier approach only enables classification of perceptual or cognitive states. It does not permit reconstruction of the stimuli or cognitive state that evoked the measured brain activity.